Motor vehicles are the major source of environmental air pollution through the combustion of lead-containing gasolines. People who live in the areas with heavy traffic usually have the higher blood lead levels. This study was to investigate the lead level between the maternal blood and their infants cord blood. Immediatly after Placental delivary, the sampls of cord blood and maternal venous blood were obtained randomly from 14 infants whose mothers had spent their entire pregnancy in Seoul. Lead concentration was determined by the dithizone method. The results obtained were summarized as follows: 1. Hemoglobin, Hct and RBC were significantly higher in cord blood than in the maternal blood, by 36%, 54.9%, 36.9% respectively. 2. MCV in cord blood was higher than that in maternal blood by 13.8%. But MCH and MCHC were lower than those in maternal blood, by 9.7%, 3.3% respectively. The differences were statistically significant. 3. Lead concentration of cord blood (23.93 μg%) was higher than that in maternal blood (21.93 μ%) by 9.1%.